<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <button id="btn">支付</button>
  <script>
    var btn = document.getElementById('btn');
    btn.onclick = function () {
      const xhr = new XMLHttpRequest();

      xhr.open('get','http://localhost:8000/v1/alipay');
      xhr.setRequestHeader('Content-type','application/x-www-form-urlencoded');
      xhr.responseType = 'json'
      xhr.send();

      xhr.onreadystatechange = function(){
        if(xhr.readyState==4){
          if(xhr.status>=200&&xhr.status<300){
            
            var result = xhr.response;
            // console.log(result.data);
            window.location.href = result.data
          }
        }
      }
    }
  </script>
</body>

</html>